1. Field of the Invention
The invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing and a method of manufacturing the same.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk device. A composite thin film magnetic head is widely used as the thin film magnetic head. The composite thin film magnetic head has a laminated structure comprising a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading. MR elements include an AMR element utilizing an anisotropic magnetoresistive (AMR) effect and a GMR element utilizing a giant magnetoresistive (GMR) effect. Methods of improving the performance of the reproducing head include a method in which an MR film is changed from an AMR film to a material having excellent sensitivity to magnetic resistance, such as a GMR film; a method in which a pattern width of the MR film, particularly, an MR height is appropriately set; and so on. The MR height means a length (height) of the MR element between the end thereof close to an air bearing surface and the opposite end thereof. The MR height is controlled in accordance with an amount of air bearing surface to be polished in working the air bearing surface. The air bearing surface means the surface of the thin film magnetic head facing a magnetic recording medium. The air bearing surface is sometimes called a track surface.
On the other hand, the improvement in the performance of the recording head is also sought in accordance with the improvement in the performance of the reproducing head. Factors for determining the performance of the recording head include a throat height (TH). The throat height means the length (height) of a magnetic pole portion between the air bearing surface and an edge of an insulating layer for electrically isolating thin film coils for generating a magnetic flux. A reduction in the throat height is desired for the improvement in the performance of the recording head. The throat height is also controlled in accordance with the amount of air bearing surface to be polished in working the air bearing surface.
The increase in a recording density of the performance of the recording head requires the increase in a track density of the magnetic recording medium. For this purpose, it is necessary to implement the recording head having a narrow track structure. In this structure, a bottom pole and a top pole are formed on the bottom and the top of a write gap, respectively, with the write gap sandwiched therebetween, and the bottom and top poles have a narrow width of from a few microns to the submicron order on the air bearing surface. Technology for fabricating a semiconductor is used in order to achieve this structure.
One example of the method of manufacturing the composite thin film magnetic head will be now described as one example of the method of manufacturing the thin film magnetic head of the related art with reference to FIGS. 32 to 37.
In this manufacturing method, first, as shown in FIG. 32, an insulating layer 102 made of alumina (Al2O3), for example, is deposited with a thickness of about 5 xcexcm to 10 xcexcm on a substrate 101 made of altic (Al2O3 and TiC), for example. Then, a lower shield layer 103 for the reproducing head is formed on the insulating layer 102. Then, alumina, for example, is sputter deposited with a thickness of 100 nm to 200 nm on the lower shield layer 103, whereby a shield gap film 104 is formed. Then, an MR film 105 for constituting the MR element for reproducing is formed with a thickness of tens of nanometers on the shield gap film 104. The MR film 105 is patterned into a desired shape by high-accuracy photolithography. Then, a lead layer (not shown) for functioning as a lead electrode layer to be electrically connected to the MR film 105 is formed on both sides of the MR film 105. Then, a shield gap film 106 is formed on the lead layer, the shield gap film 104 and the MR film 105, whereby the MR film 105 is embedded in the shield gap films 104 and 106. Then, an upper shield-cum-bottom pole (hereinafter referred to as a bottom pole) 107 made of a magnetic material for use in both of the reproducing and recording heads, e.g., permalloy (NiFe) is formed on the shield gap film 106.
Then, as shown in FIG. 33, a write gap layer 108 made of an insulating film, e.g., an alumina film is formed on the bottom pole 107. Thin film coil 110 made of, for example, copper (Cu) for an inductive recording head is formed on the write gap layer 108 by plating method, for example. Then, a photoresist layer 111 is formed into a predetermined pattern by the high-accuracy photolithography so that the thin film coil 110 may be coated with the photoresist layer 111. Then, heat treatment takes place at a temperature of, for instance, 250xc2x0 C. in order to provide planarization of the thin film coil 110 and insulation among the thin film coil 110. Then, thin film coil 112 made of, for example, copper is formed on the photoresist layer 111. A photoresist layer 113 is formed so as to cover the thin film coil 112.
Then, as shown in FIG. 34, the write gap layer 108 is partially etched at the rear of the thin film coils 110 and 112 (on the right side in FIG. 34) in order to form a magnetic path, whereby an opening 108a is formed. Then, an upper yoke-cum-top pole (hereinafter referred to as a top pole) 114 made of the magnetic material for the recording head, e.g., permalloy is selectively formed on the write gap layer 108 and a photoresist layer 113. The top pole 114 is in contact with and magnetically coupled to the bottom pole 107 in the above-mentioned opening 108a. Then, the write gap layer 108 and the bottom pole 107 are etched by about 0.5 xcexcm by means of ion milling using the top pole 114 as a mask. Then, an overcoat layer 115 made of alumina, for example, is formed on the top pole 114. Finally, a slider is machined, whereby a track surface (air bearing surface) 120 of the recording head and the reproducing head is formed. As a result, the thin film magnetic head is completed.
FIGS. 35 to 37 show the structure of the completed thin film magnetic head. FIG. 35 shows a cross section of the thin film magnetic head perpendicular to the air bearing surface 120. FIG. 36 shows an enlarged view of the cross section of the magnetic pole portion parallel to the air bearing surface 120. FIG. 37 shows a plan view. FIG. 34 corresponds to the cross section along line XXXIVAxe2x80x94XXXIVA of FIG. 37. The overcoat layer 115 is not shown in FIGS. 35 to 37.
To improve the performance of the thin film magnetic head, it is important to precisely form a throat height TH, an apex angle xcex8, a pole width P2W and a pole length P2L shown in FIGS. 35 and 36. The apex angle xcex8 means the angle between a line tangent to side surfaces of the photoresist layers 109, 111 and 113 close to the track surface and an upper surface of the top pole 114. The pole width P2W defines a recording track width on the recording medium. The pole length P2L represents the thickness of the magnetic pole. In FIGS. 35 and 37, a xe2x80x98TH0 positionxe2x80x99 means the edge of the insulating layer (the photoresist layer 109) under the thin film coils 110, close to the track surface. The TH0 position indicates a reference position 0 of the throat height TH.
The structure, in which the respective partial side walls of the top pole 114, the write gap layer 108 and the bottom pole 107 are vertically formed in self-alignment as shown in FIG. 36, is called a trim structure. This trim structure allows a prevention of the increase in an effective track width resulting from a spread of the magnetic flux generated during the writing of data on the narrow track. As shown in FIG. 36, a lead layer 122 for functioning as the lead electrode layer to be electrically connected to the MR film 105 is formed on both sides of the MR film 105. The lead layer 121 is not shown in FIGS. 32 to 35.
FIG. 38 shows a plan structure of the top pole 114. As shown in this drawing, the top pole 114 has a yoke portion 114a occupying most of the top pole 114, and a pole chip portion 114b having a substantially uniform width W100 as the pole width P2W. An outer edge of the yoke portion 114a forms an angle a with the surface parallel to the air bearing surface 120 at a coupling portion between the yoke portion 114a and the pole chip portion 114b. Moreover, the outer edge of the pole chip portion 114b forms an angle xcex2 with the surface parallel to the air bearing surface 120 at the above-mentioned coupling portion. In this case, xcex1 is about 45 degrees for example, and xcex2 is 90 degrees. The width of the pole chip portion 114b defines the recording track width on the recording medium. The pole chip portion 114b includes a portion F at the front of the TH0 position (close to the air bearing surface 120) and a portion R at the rear of the TH0 position (close to the yoke portion 114a). As can be seen from FIG. 35, the portion F extends on the flat write gap layer 108, and the portion R and the yoke portion 114a extend on a coil portion (hereinafter referred to as an xe2x80x9capex portionxe2x80x9d) which is coated with the photoresist layers 109, 111 and 113 and rises mountainously.
The shape of the top pole is described in Japanese Patent Laid-open No. 8-249614, for example.
The pole width P2W requires to be precisely formed in order to determine the track width of the recording head. More particularly, microfabrication for reducing the pole width P2W of the top pole to 1.0 xcexcm or less in dimension has been recently required in order to enable recording at high surface density, that is, in order to form the recording head having the narrow track structure.
Frame plating method is used as the method of forming the top pole, as disclosed in Japanese Patent Laid-open No. 7-262519, for instance. To form the top pole 114 by using the frame plating method, a thin electrode film made of permalloy, for example, is first formed over the apex portion by sputtering, for example. Then, the electrode film is coated with a photoresist. The photoresist is patterned by photolithography process, whereby a frame for plating is formed. Then, the top pole 114 is formed by the plating method using the preformed electrode film as a seed layer.
By the way, the height of the apex portion differs from that of the remaining portion by 3 xcexcm to 4 xcexcm or more, for example. This apex portion is coated with the photoresist with a thickness of 3 xcexcm to 4 xcexcm. Assuming that the photoresist on the apex portion needs a film thickness of 3 xcexcm or more at the minimum, a photoresist film of, for example, 4 xcexcm to 6 xcexcm or more thick is formed under the apex portion because the fluid photoresist collects at the lower place.
As described above, a formation of the narrow track requires the formation of a frame pattern of about 1.0 xcexcm wide by the photoresist film. That is, a micro-pattern of 1.0 xcexcm or less in width must be formed by the photoresist film of 4 xcexcm to 6 xcexcm or more in thickness. However, it is extremely difficult for a manufacturing process to form such a thick photoresist pattern with a narrow pattern width.
Moreover, during exposure for the photolithography, a light for the exposure is reflected by an underlying electrode film serving as the seed layer. The photoresist is exposed to this reflected light. This causes deformation or the like in the photoresist pattern. Thus, a sharp and precise photoresist pattern cannot be obtained. Consequently, the top pole cannot be formed into a desired shape, e.g., the side wall of the top pole is rounded in shape. More particularly, when an attempt is made to further reduce the pole width P2W to W100A as shown in FIG. 39, it is more difficult to obtain this desired width W100A. This occurs for the following reason. In the portion R of the pole chip portion 114b extending on the apex portion, the light, which is reflected and returned by the underlying electrode film, includes not only the vertically reflected light but also the light that is obliquely or transversely reflected from an inclined surface of the apex portion. These reflected lights have an influence upon the exposure of the photoresist layer. As a result, a photoresist pattern width for defining the pole width P2W is larger than an intended value. Therefore, the portion R has the shape shown by a solid line in FIG. 39. The width of the portion F of the pole chip portion 114b at the front of the TH0 position is a very important factor for defining the track width on the recording medium. Thus, an intended minute track width cannot be obtained when the width of the portion F is larger than the above-mentioned value W100A.
Such a problem similarly exists in the magnetic head described in Japanese Patent Laid-open No. 8-249614 mentioned above. In the magnetic head described in this publication, the pole width is gradually changed from the TH0 position toward the yoke portion. Thus, the light, which is obliquely or transversely reflected from the inclined surface of the apex portion, has the influence upon the exposure of the photoresist layer. Due to this influence, the width of the portion at the front of the TH0 position cannot be precisely controlled.
Moreover, as shown in FIG. 39, the portion R of the pole chip portion 114b between the TH0 position and the coupling portion to the yoke portion 114a has substantially the same width as the width of the portion F at the front of the TH0 position. Thus, the portion R has a small cross-sectional area. Thus, the magnetic flux from the yoke portion 114a is saturated in the portion R. Thus, the magnetic flux cannot sufficiently reach to the portion F for defining the track width. Therefore, overwrite properties, i.e., the properties of overwriting the data on the data already written on the recording medium is as low as about 10 dB to 20 dB, for example. Consequently, there is a problem of being unable to ensuring sufficient overwrite properties.
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a thin film magnetic head and a method of manufacturing the same, which can precisely control the pole width and can obtain sufficient overwrite properties even when the pole width is reduced.
A thin film magnetic head of the invention comprises: two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein one of the two magnetic poles includes a first magnetic layer portion extending away from the recording-medium-facing surface along the gap layer and having a uniform width for defining a recording track width on the recording medium, the insulating layer includes a first insulating layer having a reference edge for defining the edge on a recording-medium-facing surface side of the insulating layer and formed in a region between the first magnetic layer portion and the thin film coils along the gap layer, and a second insulating layer for embedding the thin film coils, and one of the two magnetic layers including the one of the two magnetic poles includes a second magnetic layer portion covering at least the first insulating layer and magnetically coupled to the first magnetic layer portion.
A method of manufacturing a thin film magnetic head of the invention is a method of manufacturing a thin film magnetic head having two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers. The method comprises the steps of forming one of the two magnetic poles so as to include a first magnetic layer portion extending away from the recording-medium-facing surface along the gap layer and having a uniform width for defining a recording track width on the recording medium; forming the insulating layer so as to include a first insulating layer and a second insulating layer, the first insulating layer having a reference edge for defining the edge on a recording-medium-facing surface side of the insulating layer, the first insulating layer being located in a region between the first magnetic layer portion and the thin film coils along the gap layer, the second insulating layer embedding the thin film coil; and forming one of the two magnetic layers including the one of the two magnetic poles so as to include a second magnetic layer portion covering at least the first insulating layer and magnetically coupled to the first magnetic layer portion.
In the thin film magnetic head or the method of manufacturing the same of the invention, the recording track width on the recording medium is defined by the first magnetic layer portion included in one of the two magnetic poles and having a uniform width. The insulating layer for insulating the thin film coils includes the first insulating layer and the second insulating layer. The first insulating layer is formed in the region between the first magnetic layer portion and the thin film coils along the gap layer. The surface of the region near the edge on a recording-medium-facing surface side of the first insulating layer forms a slope. The edge of the first insulating layer serves as the reference edge for defining the edge on a recording-medium-facing surface side of the insulating layer for insulating the thin film coils. The second insulating layer is used to embed the thin film coils. One of the two magnetic layers, which includes the one magnetic pole, includes the second magnetic layer portion. At least the first insulating layer covers the second magnetic layer portion. The second magnetic layer portion is magnetically coupled to the first magnetic layer portion.
In the thin film magnetic head or the method of manufacturing the same of the invention, the one of the two magnetic poles may further include a third magnetic layer portion magnetically coupled to the first magnetic layer portion, extending in a direction opposite to the recording-medium-facing surface and having a width greater than the width of the first magnetic layer portion. In this case, it is preferable that the third magnetic layer portion is surrounded on at least three sides by the second magnetic layer portion. Furthermore, the first magnetic layer portion may be surrounded on at least three sides by the second magnetic layer portion.
Moreover, in the thin film magnetic head or the method of manufacturing the same of the invention, it is preferable that the magnetic pole including the first magnetic layer portion and the third magnetic layer portion has a T-shaped plan shape. Alternatively, it is preferable that the width of the third magnetic layer portion is gradually increased as it is farther from the recording-medium-facing surface.
Moreover, in the thin film magnetic head or the method of manufacturing the same of the invention, it is preferable that the first magnetic layer portion and the third magnetic layer portion extend in contact with the gap layer. In this case, it is preferable that the first magnetic layer portion and the third magnetic layer portion are formed through dry process and the second magnetic layer portion is formed through electroplating process. Furthermore, in this case, the first magnetic layer portion and the third magnetic layer portion can be made of a material containing iron nitride, and the second magnetic layer portion can be made of a material containing nickel and iron.
Moreover, in the thin film magnetic head or the method of manufacturing the same of the invention, the one of the two magnetic poles may further include at least two fourth magnetic layer portions magnetically coupled to the third magnetic layer portion, separated in a direction of the recording track width, and extending in the region opposite to the recording-medium-facing surface of the third magnetic layer portion. The fourth magnetic layer portions may extend in contact with the gap layer, or the fourth magnetic layer portions may extend on the first insulating layer. Moreover, each of the fourth magnetic layer portions may be surrounded on at least three sides by the second magnetic layer portion.
Moreover, in the thin film magnetic head or the method of manufacturing the same of the invention, the first insulating layer and the second insulating layer may be integrally formed by the same process using the same material.
Moreover, in the thin film magnetic head or the method of manufacturing the same of the invention, the one of the two magnetic layers may further include a fifth magnetic layer portion partly covering the thin film coils with the second insulating layer in between. Furthermore, in this case, the second magnetic layer portion and the fifth magnetic layer portion may be integrally formed by the same process using the same material.
A method of manufacturing a thin film magnetic head according to another aspect of the invention is a method of manufacturing a thin film magnetic head having two magnetic layers magnetically coupled to each other and having two magnetic poles which face each other with a gap layer in between and are to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers. The method comprises the steps of forming one of the two magnetic poles on the gap layer so as to include a portion extending away from the recording-medium-facing surface and having a uniform width for defining a recording track width on the recording medium; forming a reference-defining insulating layer in the region opposite to the recording-medium-facing surface on the gap layer, the reference-defining insulating layer constituting a part of the insulating layer and having a reference edge for defining the edge on a recording-medium-facing surface side of the insulating layer, the surface of the reference-defining insulating layer near the reference edge forming a slope; forming a coupling magnetic layer so as to cover at least the reference-defining insulating layer, the coupling magnetic layer constituting a part of one of the two magnetic layers including the one of the two magnetic poles, and being magnetically coupled to the magnetic pole formed on the gap layer; forming the thin film coils along the gap layer; and embedding the thin film coils in a embedding insulating layer constituting another part of the insulating layer.
In the method of manufacturing the thin film magnetic head according to another aspect of the invention, first, one of the two magnetic poles is formed on the gap layer. The one of the two magnetic poles includes the portion extending away from the recording-medium-facing surface and having a uniform width for defining the recording track width on the recording medium. Then, the reference-defining insulating layer constituting a part of the insulating layer for insulating the thin film coils is formed in the region opposite to the recording-medium-facing surface on the gap layer. The reference-defining insulating layer has the reference edge for defining the edge on a recording-medium-facing surface side of the insulating layer. The surface of the reference-defining insulating layer near the reference edge forms a slope. Then, the coupling magnetic layer constituting a part of one of the two magnetic layers including the one of the two magnetic poles is formed so as to cover the reference-defining insulating layer. The coupling magnetic layer is magnetically coupled to the magnetic pole formed on the gap layer. Then, the thin film coils are formed along the gap layer. The thin film coils are embedded in the embedding insulating layer constituting another part of the insulating layer.
In the method of manufacturing the thin film magnetic head according to another aspect of the invention, the magnetic pole can be formed through dry process, and the coupling magnetic layer can be formed through electroplating process. In this case, it is preferable that the one of the two magnetic poles is made of a material containing iron nitride and the coupling magnetic layer is made of a material containing nickel and iron.
In the method of manufacturing the thin film magnetic head according to another aspect of the invention, the method further comprises the steps of flattening the surfaces of at least both of the magnetic pole and the embedding insulating layer after forming the embedding insulating layer; and forming a yoke magnetic layer so as to partly covering the thin film coils with the flattened embedding insulating layer in between, the yoke magnetic layer constituting another part of the magnetic layer including the one of the two magnetic poles and being magnetically coupled to the one of the magnetic poles.